Multi-purpose blowing apparatus

ABSTRACT

A multi-purpose blowing apparatus is provided, in particular for use in the agricultural field and the like, comprising an engine ( 2 ), a fan wheel ( 3 ) moved by the engine and adapted to generate a delivery air flow ( 4 ), and a volute header ( 5 ) surrounding said fan wheel ( 3 ) and adapted to convey said delivery flow ( 4 ) towards use means; said fan wheel comprises a support element ( 13 ) presenting a first a second face ( 13   a,    13   b ) mutually opposite and respectively invested by a first and a second air flows ( 10, 11 ) coming from mutually opposite directions, a predetermined number of blades emerging from said second face ( 13   a ) and at least one air passage ( 13   c ) provided in the support element ( 13 ) and adapted to direct at least said first air flow ( 10 ) through said support element ( 13 ).

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation in part of applicant's copending application Serial No. 09/621.017, filed on Jul. 21, 2000.

FIELD AND BACKGROUND OF THE INVENTION

[0002] The present invention relates to a multi-purpose blowing apparatus, in particular for use in the agricultural field and the like, comprising an engine, a centrifugal fan wheel moved by the engine and adapted to generate a radial air flow, a volute header enclosing said fan wheel and adapted to convey said radial flow at least partly towards the intended use means.

[0003] It is known that in many applications, such as in the agricultural field, when cleaning of streets and pavements or grasslands is concerned, as well as for other similar application fields, portable blowing apparatus are used which are adapted to produce a strong air jet.

[0004] This air jet can be employed for spraying or atomizing anticryptogamic or manuring liquids held in small tanks associated with the blowing apparatus itself, or may constitute an air current of appropriate force for removal and displacement of leaves or other light material from road surfaces or grasslands.

[0005] The blowing apparatus generally comprises a two-stroke inner combustion engine moving a centrifugal fan wheel adapted to generate a substantially radial delivery air flow. The fan wheel is externally surrounded by a volute header adapted to convey the air flow at least partly towards the intended use means, which may consist for example of a flexible hose adapted to be gripped by an operator responsible for the apparatus.

[0006] In the known art, the centrifugal fan wheel bears a number of blades which, during suction, generate a single substantially axial air flow converging towards the blades themselves, on the opposite side with respect to the engine.

[0007] Part of the delivery air flow is deviated from the provided main use and conveyed towards the engine sometimes contained at least partly in a casing, for cooling of the engine itself.

[0008] The known art briefly described above has some important drawbacks.

[0009] In fact, first of all, it is characterized by a non-optimal yield because the delivery air flow is not completely conveyed towards the use means provided for the blowing apparatus, but it is partly deviated for engine cooling. Part of the used energy is therefore employed for merely achieving a correct engine operation and the air flow really utilized has a smaller flow rate than that emitted from the wheel fan.

[0010] It should be also pointed out that engine cooling by means of an overpressure air flow is often of poor efficiency; in fact, due to flow resistance to which the air flow is submitted while passing through often tortuous passageways between the engine and casing, overpressure is reduced or eliminated, which will therefore stop or at all events decrease the air outflow.

[0011] It is to be added that if the engine is not provided with a casing for improving cooling thereof, it produces a strong noise often higher than the limits that in some countries are allowed by regulations against sound pollution.

[0012] At all events, the blowing apparatus in accordance with the known art, even if it is provided with an engine-holding casing, often does not succeed in maintaining the engine noise within limits of acceptability because the cooling air flow, after impinging on the engine, flows out of the casing together with sound waves.

[0013] It is also to be noted that the air flow dedicated to engine cooling, heated by heat exchange with said engine, forms a troublesome hot air mass often directed towards the operator or other people near him/her.

[0014] Finally, it should be recognized that the fan wheel used in the known art which has a single axial-suction flow is asymmetric from a mechanical and hydraulic point of view and therefore it can be easily submitted to vibrations giving rise to a further noise source.

SUMMARY OF THE INVENTION

[0015] Under this situation, the technical task underlying the present invention is to conceive a multi-purpose blowing apparatus capable of substantially obviating the mentioned drawbacks.

[0016] Within the scope of this technical task, it is an important object of the invention to devise a blowing apparatus having a high yield and operating efficiency.

[0017] Another important object of the invention is to devise a blowing apparatus capable of improving efficiency in cooling the engine provided therein.

[0018] A further object is to provide a blowing apparatus emitting a reduced level of noise to the surrounding atmosphere.

[0019] A still further object of the invention is to devise a blowing apparatus capable of exclusively producing an air current to the outside, the direction of which is directly controlled by the operator without generating any troublesome hot air current directed against the operator or other people.

[0020] The technical task mentioned and the objects specified are substantially achieved by a multi-purpose blowing apparatus wherein a centrifugal fan wheel has a support element presenting a first and a second face (mutually opposite) invested by respective air flows coming from mutually opposite directions, a predetermined number of blades emerging from one of these two faces and at least one air passage provided in the support element and adapted to direct the air flow impacting on the first face at least partly through the support element itself.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Description of a preferred embodiment of a multi-purpose blowing apparatus in accordance with the invention is now given hereinafter, by way of non-limiting example, with reference to the accompanying drawings, in which:

[0022]FIG. 1 is a section taken along an axial plane of the apparatus in accordance with the invention;

[0023]FIGS. 2a and 2 b are perspective views of the apparatus in FIG. 1;

[0024]FIGS. 3 and 4 are perspective views of a centrifugal fan wheel associated to the apparatus of FIGS. 1 and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0025] with reference to the drawings, the multi-purpose blowing apparatus in accordance with the invention is generally identified by reference numeral 1.

[0026] It comprises an engine, which can conveniently be an internal combustion engine 2, provided with at least one cylinder and having cooling blades (see FIG. 1). It should be however clear that, according to the present invention, other engine types (e.g. electrical engines) may be fitted in the apparatus, depending on various requirements.

[0027] A driving shaft of the engine 2 moves a centrifugal fan wheel 3 coupled therewith and capable of generating a radial delivery air flow (identified by arrows 4 in FIG. 1).

[0028] The air flow is conveyed towards provided use means by a volute header 5 externally surrounding the fan wheel 3; in other words, the apparatus 1 according to the present invention may comprise differently shaped use means for blowing out the compressed air flow (that is, the radial delivery air flow 4), which are operatively associated at least with the centrifugal fan wheel 3 and are adapted to convey an exhaust air flow generated by the centrifugal fan wheel 3 itself.

[0029] The above cited use means generally comprises a flexible hose 6, direction of which can be controlled by an operator.

[0030] Optionally, the cited use means may comprise a tank 7 for liquid injection in the airflow. This liquid, which can be atomized in the air flow, is housed in the tank 7 and is suitably admitted to the hose 6 in operative conditions.

[0031] In an original manner, the centrifugal fan wheel 3 has a predetermined number of blades adapted, during suction, to generate substantially axial air flows (i.e. flows directed parallelly of the engine axis 2 a) coming together from opposite directions (that is, a first axial flow identified by arrows 10 and a second axial flow represented by arrows 11).

[0032] It is to be noted that the axis 2 a can also be considered as a rotation axis about which the centrifugal fan wheel 3 rotates during operation.

[0033] Engine 2 is disposed along the path of said substantially axial first flow 10 so that the latter, by externally grazing said engine 2, practically defines a sucking flow for engine cooling. Such a sucking cooling flow is suitably generated by the centrifugal fan wheel 3, in a manner which will be herebelow clarified.

[0034] From a structural standpoint, the centrifugal fan wheel 3 (see FIGS. 1, 3 and 4) comprises a support element 13 presenting a first face 13 a and a second face 13 b opposite to said first face 13 a.

[0035] The first and the second faces 13 a, 13 b are respectively invested by a first and a second air flows 10, 11 coming from mutually opposite directions; it is now to be noted that the first air flow is essentially the above defined sucking cooling flow (which circulates in the left-hand side of the apparatus section depicted in FIG. 1), while the second air flow 11 enters the apparatus from the right-hand side.

[0036] Therefore, it can be seen that the first air flow 10 impacts on the first face 13 a, while the second air flow 11 impacts against the second face 13 b.

[0037] The centrifugal fan wheel 3 also comprises a predetermined number of blades, emerging from the second face 13 b (but if required, blades can be provided alternatively on the first face 13 a, or even on both the two faces 13 a and 13 b), whose relative displacement and shaping will be further discussed.

[0038] Advantageously, the centrifugal fan wheel 3 comprises at least one air passage 13 c, which is provided in the support element 13 and is adapted to direct at least the first air flow 10 (investing the first face 13 a) at least partly through the support element 13 itself. In other words, the air passage 13 c is aerodynamically connected to the blades so that the blades themselves and the air passage 13 c cooperatively define the radial delivery air flow 4, the latter advantageously resulting from the mixing and/or the confluence of the first and the second air flows 10, 11.

[0039] Actually, thanks to the air passage 13, the air sucked from the “engine side” of the apparatus 1 is fully mixed with the air entering the apparatus 1 from the “opposite” side of the apparatus 1 (that is, the side which is opposite to the engine 2). In this way, no airflow losses are generated and therefore the maximum efficiency for the centrifugal fan wheel 3 can be achieved.

[0040] Moreover, the provision of blades on one face (the second face 13 a) and the provision for adequate means for mixing and compressing air coming also from the opposite side of the support element 13 c, allow to reduce noise generation, as well as optimizing the aerodynamic efficiency of the centrifugal fan wheel 3. Indeed, the sound waves generated by the apparatus' moving parts are forced to move against the air flow. Moreover, thanks to the presence of the air passage 13 c, destructive acoustic interference takes place in the centrifugal fan wheel 3 area.

[0041] In the apparatus according to the present invention, the first and the second air flows 10, 11 are substantially axial (that is, parallel to the axis 2 a, at least in proximity of the centrifugal fan wheel 3) and more in particular they are opposite to each other at least at the centrifugal fan wheel 3 entry.

[0042] Looking more closely at the centrifugal fan wheel 3 structure, it is to be noted that the support element 13 comprises a hub portion 14, which is pivotally engaged about the rotation axis 2 a, a central portion 15 radially extending from the hub portion 14 and a peripheral portion 16 axially displaced along the rotation axis 2 a with respect to the central portion 15.

[0043] Conveniently, the air passage 13 c is defined by an ideal surface lying between the central portion 15 and the peripheral portion 16 (this surface is essentially transverse to the surfaces defined by the central and peripheral portions 15, 16 of the support element 13).

[0044] More in general, according to the present invention the air passage 13 c is defined in the support element 13 in a way such that mixing of air flows coming together from different directions is allowed: consequently, other shapes of the support element can be employed (e.g. a frusto-conical or pyramid-shaped support element, or whatsoever similar shape), provided that at least an air passage 13 c, which can simply be a substantially plan slot, exists on the support element 13 itself.

[0045] Referring to FIGS. 3 and 4, it can be seen that in the preferred embodiment shown the central portion 15 is lying on a first plane transverse to the rotation axis 2 a, while the peripheral portion 16 is lying on a second plane substantially parallel to the cited first plane and axially displaced (along the rotation axis 2 a) by a predetermined distance.

[0046] In this way, the air passage 13 c is essentially defined by a cylindrical surface, which is substantially parallel to the axis 2 a and lies between the central portion 15 and the peripheral portion 16.

[0047] Even more in particular, it can be seen that in the embodiment shown in FIGS. 3 and 4, the central portion 15 is essentially disc-shaped, while the peripheral portion 16 is ring-shaped.

[0048] Thanks to the above described structure, the first air flow 10 impacts against the faces without blades of the central and of the peripheral portions 15, 16 and is drawn through the air passage 13 c, where the aerodynamic actions exerted by the blades mix the first air flow 10 with the second air flow 11 arriving from the support element's opposite faces.

[0049] Looking more closely at the blades, it can be seen that a peculiar structure can be defined by the present invention: actually, the blades can comprise first blades 8 having a first root portion 8 a located on the central portion 15 (preferably, near to the hub portion 14, so as to maximize efficiency) and a first tip portion 8 b radially opposite to the first root portion 8 a and located on the peripheral portion 16 (near the outermost portion of the ring-shaped peripheral portion 16, as visible in FIGS. 3 and 4). These first blades 8 may have a predetermined axial height (that is, a development along the direction of the axis 2 a) which can be at least equal to the height of the air passage 13 c and more in general equal to a predetermined first height.

[0050] The apparatus according to the present invention may also comprise second blades 9: these second blades 9 have a second root portion 9a located in correspondence of said air passage 13 c (and more precisely, the second root portion is axially spanning through the air passage 13 c, as shown in the preferred embodiment—see FIGS. 3 and 4) and a second tip portion 9 b radially opposite to the second tip portion 9 a, similarly to what stated above, even the second tip portion 9 b is located on the peripheral portion 16, and more precisely near the outermost portion of the ring-shaped peripheral portion 16.

[0051] The second blades 9 may have an axial development, along the axis 2 a, equal to a second height which can be less than the first height of the first blades 8. As clearly shown in the preferred embodiment (once again, FIGS. 3 and 4), the second blades 9 may have an axial development equal to the axial development of the air passage 13 c.

[0052] Advantageously, from a hydraulic point of view, the first blades 8 are such designed that during suction they generate the first air flow 10 with a flow rate adapted to completely cool the engine. However, whenever the second blades 9 are present, even their design features can be chosen in order to contribute to generate the required first air flow 10 for complete engine cooling.

[0053] In other words, the resulting flow rate, induced in the apparatus 1 from various intake ports and then conveyed to a single exhaust port (represented by the use means), may advantageously determined by all the blades' series 8 and/or 9, not only in qualitative terms (turbulence degree) but also in and quantitative terms (numeric value of resulting flow rate).

[0054] The radial delivery air flow 4 (resulting from the mixing of the air flows 10 and 11) can be completely conveyed by the volute header 5 towards the hose 6. Practically, due to the described solution, it is therefore not necessary to draw part of this radial delivery flow 4 (produced by the centrifugal fan wheel 3) in order to direct it towards the engine 2 for cooling purposes.

[0055] The first and second blades 8, 9, during suction generate an air flow returned towards the fan wheel from a feeding opening 5 a defined by the volute header 5. The feeding opening 5 a is placed opposite to the first blades 8 and extends coaxially with the engine axis 2 a at a region radially internal to the second blades 9.

[0056] It is further to be pointed out that engine 2 is completely enclosed in a casing 12 provided with ventilation openings 12 a to be passed through by at least the first air flow 10.

[0057] Casing 12 has a shell-like conformation and is connected at an attachment edge 12 b thereof with the volute header 5. The ventilation openings 12 a are all disposed in a bottom wall 12 c of the casing substantially transverse to the engine axis 2 a and they are positioned on the opposite side with respect to the attachment edge 12 b. In particular, part of the ventilation openings 12 a are disposed in a region of the bottom wall 12 c substantially close to the cooling blades 2 b of engine 2 so that the first air flow 10 during suction impinges on the engine surface (where a greater heat removal is required).

[0058] Finally, all the casing walls are particularly arranged for sound insulation to reduce spreading of noise to the surrounding atmosphere to the highest degree. At this purpose, in FIG. 1 it can be seen that the engine-holding casing 12 may comprise walls adapted to sound insulation.

[0059] From a structural point of view, the noise suppression capability is pursued by a predetermined number of internal walls 17a, which cooperatively define an acoustic labyrinth adapted to hamper the sound diffusion towards the external environment. The relative positioning of the internal walls 17 a can be determined in order to optimize noise suppression: for example, as seen in FIG. 1 the internal walls 17 a may encircle the engine 2 a so that noise produced from the latter is reflected and substantially contained within the casing 12.

[0060] In order to enhance even more the noise suppression capability, the apparatus 1 may also comprise air-permeable acoustic filters 17 b, which are associated to the engine-holding casing 12 and which are at least partly immersed in the first and/or second air flows 10, 11) (within the engine-holding casing 12 itself). Looking at FIG. 1, it can be noted that these acoustic filters 17 b are placed between external walls and internal walls 17 a of the engine-holding casing 12. Conveniently, the porosity and the physical properties of the acoustic filters 17 b may be chosen in order to allow the required air flow; at the same time, according to the present invention, a great flexibility in positioning the acoustic filters 17 b can be achieved: actually, provided that satisfactory first and/or second air flows 10 and/or 11 is/are granted, the acoustic filters 17 b can be placed substantially anywhere in the apparatus 1.

[0061] For best ergonomy in use, the apparatus 1 according to the present invention may comprise means for back-holding 18; these means 18 are adapted to engage the apparatus 1 to an operator's back and generally comprise a predetermined number of suspenders 18 a suitably connected to the apparatus 1. Whenever required, the back-holding means 18 may also comprise a framework 18 b, which is connected to the apparatus 1 and bears the suspenders 18 a.

[0062] The invention achieves important advantages.

[0063] In fact, first of all, it should be pointed out that utilization of one of the sucking air flows for cooling the engine increases the apparatus yield to an important degree as compared with apparatuses of the known art because all the air coming out of the fan wheel is conveyed towards the intended use means.

[0064] It will be further recognized that also efficiency of the engine cooling is improved, since the centrifugal fan wheel creates a vacuum within the wheel casing, which vacuum is adapted to ensure circulation of the air entering from the outside and reaching each region around the engine without stagnation regions being formed.

[0065] It should be noted that vacuum within the casing is not adversely affected by a possible reduction in the opening ports required for suction: because of this fact, noise from the apparatus is further limited, said noise being made already less strong due to air suction in the engine region and therefore to tendency of the sound waves to remain confined within the engine casing.

[0066] Due to the presence of cooling openings exclusively at the bottom region of the casing, the residual outgoing sound waves are oriented towards the side opposite to the operator's closest side.

[0067] Moreover, the operator is not impinged on by any hot air mass, because the sucking air flow heated by the engine, in addition to being mixed with the cold air of the second sucking flow, is at all events conveyed far away, through the flexible hose into which it flows.

[0068] Finally, it will be recognized that the centrifugal fan wheel with two mutually cooperating blade series gives rise to a significant noise reduction, offering greater reliability, without on the other hand requiring heavy axial-stop systems. 

1. A multi-purpose blowing apparatus, in particular for use in the agricultural field and the like, comprising: an engine (2), a fan wheel (3) moved by the engine and adapted to generate a radial delivery air flow (4), and a volute header (5) surrounding said fan wheel (3) and adapted to convey said radial delivery flow (4) at least partly towards provided use means, wherein said fan wheel comprises: a support element (13) presenting a first face (13 a) and a second face (13 b) mutually opposite to said first face (13 a), said first and second faces (13 a, 13 b) being respectively invested at least by a first and a second air flows (10, 11) coming from mutually opposite directions; a predetermined number of blades emerging from said second face (13 b); and at least one air passage (13 c) provided in the support element (13) and adapted to direct at least said first air flow (10) investing said first face (13 a) at least partly through said support element (13).
 2. The apparatus s claimed in claim 1, wherein said air passage (13 c) is aerodynamically connected to said blades, the blades and the air passage (13 c) cooperatively defining said radial delivery air flow (4), said radial delivery air flow (4) substantially resulting from mixing and/or confluence of said air flows (10, 11).
 3. The apparatus as claimed in claim 1 or 2, wherein said air flows (10, 11) are substantially axial and opposite to each other at least at the centrifugal fan wheel (3) entry.
 4. The apparatus as claimed in claim 1, wherein said support element (13) comprises a hub portion (14) pivotally engaged about a rotation axis (2 a), a central portion (15) radially extending from said hub portion (14) and a peripheral portion (16) axially displaced along said rotation axis (2 a) with respect to said central portion (15), said air passage (13 c) being defined by an ideal surface lying between said central portion (15) and said peripheral portion (16).
 5. The apparatus as claimed in claim 4, wherein said central portion (15) is lying on a first plane transverse to the rotation axis (2 a), said peripheral portion (16) lying on a second plane substantially parallel to said first plane and axially displaced, along the rotation axis (2 a), by a predetermined distance, said air passage (13 c) being defined by a cylindrical surface between said central portion (15) and said peripheral portion (16).
 6. The apparatus as claimed in claim 4, wherein said blades comprise first blades (8) having a first root portion (8 a) located on the central portion (15) and a first tip portion (8 b) radially opposite to said first root portion (8 a) and located on the peripheral portion (16).
 7. The apparatus as claimed in claim 4, wherein said blades comprise second blades (9) having a second root portion (9 a) located in correspondence of said air passage (13 c) and a second tip portion (9 b) radially opposite to said second tip portion (9 a) and located on the peripheral portion (16).
 8. The apparatus as claimed in claim 1, wherein said engine (2) is disposed along the path of at least one of said first and/or second air flows (10, 11), so that at least said first air flow (10) defines an aspiration flow for engine cooling, generated by the corresponding first and/or second blades (8, 9) of said centrifugal fan wheel (3).
 9. The apparatus as claimed in claim 8, wherein said first and/or second blades (8, 9) generate said first air flow (10) for engine cooling having a flow rate adapted to complete cooling of the engine (2), so that said radial delivery air flow (4) can be completely conveyed from said volute header (5) to said provided use means.
 10. The apparatus as claimed in claim 8, comprising an engine-holding casing (12) having ventilation openings (12 a) to be passed through by said first air flow (10) for engine cooling.
 11. The apparatus as claimed in claim 10, wherein said engine-holding casing (12) has a shell-like conformation and is connected at an attachment edge (12 b) thereof with said volute header (5).
 12. The apparatus as claimed in claim 11, wherein said ventilation openings (12 a) are disposed in a bottom wall (12 c) of said casing (12) substantially transverse to the axis (2 a) of the engine (2) and positioned on the opposite side from said attachment edge (12 b).
 13. The apparatus as claimed in claim 12, wherein said ventilation openings (12 a) are placed at least partly in a region of said bottom wall (12 c) of the casing (12) substantially disposed close to said first and/or said second blades (8, 9).
 14. The apparatus as claimed in claim 6, wherein the first and/or the second blades (8, 9) during suction generate a second air flow (11) returned through at least one feeding opening (5 a) defined by said volute (5) and opposite to the first blades (8).
 15. The apparatus as claimed in claim 6, wherein said feeding opening (5 a) extends coaxially with the axis (2 a) of said engine (2), at a region radially internal at least to said second blades (9).
 16. The apparatus as claimed in claim 10, wherein said engine-holding casing (12) comprises walls adapted to sound insulation.
 17. The apparatus as claimed in claim 16, wherein said engine-holding casing (12) comprises a predetermined number of internal walls (17 a) cooperatively defining an acoustic labyrinth adapted to hamper the sound diffusion towards the external environment.
 18. The apparatus as claimed in claim 12, wherein said engine-holding casing (12) comprises air-permeable acoustic filters (17 b) at least partly immersed in the first and/or second air flows (10, 11) within the engine-holding casing (12).
 19. The apparatus as claimed in claim 1, further comprising means for back-holding (18) adapted to engage the apparatus (1) to an operator's back.
 20. The apparatus as claimed in claim 19, wherein said means for back-holding (18) comprise a predetermined number of suspenders (18 a) and a framework (18 b) connected to the apparatus (1) and bearing said suspenders (18 a). 